Pinonic and pinoylformic acid esters



Patented May 25, 1954 2,679,509 PINONIC AND PINOYLFORMIC ACID ESTERS Torsten Hasselstrom, Philadelphia, Pa.

No Drawing. Application September 15, 1950, Serial No. 185,139

1'7 Claims.

(Granted under Title 35, U. S. Code (1952),

see. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to esters of keto terpenic acids, to methods of their preparation and to their application in the plasticizing of polymers and other uses.

It is well known in the art that camphor is a. plasticizer of nitrocellulose. Numerous other terpenes have also been used for this and similar purposes; however, camphor and such othe terpenes are relatively expensive and are frequently found to be incompatible with a'pa-rticular resin.

I have found that certain esters of terpene carboxylic acids are excellent plasticizers and possess other valuable properties such as beingfungistatic.

I have further found that certain esters suitable for the purposes of present invention may be synthesized, at a price far below the price of natural or synthetic camphor, by utilizing the crude sulfate turpentine which results as a byproduct from the well-known sulfate pulp process.

It is thus an object of my invention toprovide new esters of terpene carboxylic acids.

Another object of my invention is the production of such esters and of the intermediate products, i. e. of terpene carboxylic acids, from an inexpensive industrial by-product.

A further object of my invention is the provision of plasticized cellulosic and resinous films capable of withstanding extremely low temperatures.

Still another object of my invention is the provision of fungistat-ic and low temperature resistant coating materials, such as greases, lacquers, paints, wherein terpene carbo-xylic acid esters are incorporated.

Still another object of my invention is the provision of plasticized synthetic and natural resins, natural and synthetic rubber, such as molded resins, rubber compositions, cements and adhesives, wherein terpene carboxylic esters are incorporated.

Still further objects and advantages of my invention will become apparent from the following description of the same.

Among the esters contemplated by the present invention are the esters of such monocyclic keto ei'pene carboxylic acids as, for instance, pinonic acid, pinononic acid, pinoylformic acid, which three acids are characterized by a 2,2-dimethyl cyclobutane group to which a ketogroup is attached externally of the ring, or bicyclic keto-terpene carboxylic acids such as camphenonic acid, keto camphoric acids, ketopinic acid, ketoteresantelic acid. However, other .terpene carboxylic acids and theirhomologs and analogs may be emplcyed as starting materials such as pinic acid, nopinic acid, camphoric acid, camphenic acid, and acids obtained by the oxidation of such bicyclic terpenes as fenchenes, bornylene, carene, sabinene, 'cedrene, caryophyllene, cadinene, or of their hydrogenated counterparts such as camphanes, fenchanes, apobornylane, santane, 'norcamp-hane, and acids obtained from naphthenes and their homologs and analogs and from homoterpenes. Suitable alcohols for esterifying these terpene .carboxylic acids are liquid alcohols of the type A(OH) 1 l-r'z, A being an organic residue, e. g. aliphatic alcohols, particularly those whose carbon chain has at least 5 carbon atoms, cycloaliphatic alcohols, and aromatic alcohols wherein the benzene ringand the hydroxyl group are linked by methylene; examples of suitable esterifying alcohols are amyl alcohol, hexanol, octanol, substituted glycols, .cyclohexanol, benzyl alcohol, and natural or synthetic hydroxy-terpenes such as nopol. Esterification may take place by conventional methods, such as refluxing and removal of water by excess alcohol and/or and aromatic hydrocarbon such as toluene or xylene. Conventional esterification catalysts such as benzene sulfonic acid may also be employed, particularly when steric hindrance is encountered.

It will be understood that the esters may also be produced by reacting the acid anhydride or acyl halides or reactive salts of terpene carboxylicacids with an esterifying substance; ester exchange (i. e. esterification of a terpene carboxylic acid, followed by exchange of the alcohol residue group 'for another) is also within the purview of myinvent-ion.

The followingexamples illustrate the production of some-of the pinonic acid esters contemplated by the present invention:

3 EXANIPLE I Benzyl ester of pinonic acid 150 g. alpha-pinene was emulsified by mixing in 3000 cc. of water, and 232 g. of potassium permanganate added with eflicient stirring, in portions, durin a period of about four hours. The temperature was kept below C. and the stirring continued for four hours additional. After standing overnight, the color of the permanganate had disappeared. The manganese dioxide formed in the reaction was removed by filtration, the precipitate washed with about 300 cc. of water, and the clear filtrate evaporated in a stream of carbon dioxide until approximately 500 cc. of a brown syrup remained. This residue was acidified with dilute sulfuric acid, whereby the terpene carboxylic acids separated as an upper, oily layer, which was separated by gravity from the lower aqueous layer containing potassium sulfate and free sulfuric acid. Yields of terpene oarboxylic acids, crude pinonic acid, were approximately 50% by weight of the starting material, alpha-pinene.

In order to recover maximum amounts of terpene carboxylic acids, the aqueous lower layer was extracted with ethyl ether, the ether solution dried with anhydrous sodium sulfate, and the ether distilled off, whereby the residue represents the total amount of terpene carboxylic acids produced. Instead of ethyl-ether any water-immiscible solvent may be used, in which the terpene carboxylic acids are soluble as, for instance, chloroform, tetrachloroethane, ethylenedichloride, aliphatic hydrocarbons, benzene and its homologs, aliphatic and aromatic ethers and esters. In the acidification step, hydrochloric acid, phosphoric acid, acid sodium sulfate and the like might be used instead of sulfuric acid.

'75 g. crude pinonic acid prepared as above was refluxed with an excess of benzyl alcohol and approximately cc. of toluene at about 190 C., water being continuously removed in a water trap. After several days of number of the mixture was approximately one, the mixture was steam distilled to remove excess benzyl alcohol and toluene, extracted with ether,

and after evaporating off the ether, fractionated under reduced pressure. The fraction boiling at l60-190 C. (zoo-250 was collected. The yield was 55.2 g. of refined benzyl ester of pinonic acid; refractive index n "=l.5l3'7; n =l.51l9; specific gravity di =l.0622l; melting point of the semicarbazone ll6-l1'7 C. The semicarbazone in this and the following examples was prepared by dissolving the ester, semicarbazide hydrochloride and fused sodium acetate separately in ethanol and water, combining the solutions, placing the combined solution in an ice box for a few days, precipitating the solid semicarbazone from the solution by the addition of cold water, and recrystallizing from dilute ethanol.

While potassium permanganate was employed as the oxidation reagent for turpentine in this example, other oxidizing agents which do not split the 2,2-dimethy1 cyclobutane ring of alphapinene (which is the principal constituent of turpentine) may be employed for the making of terpenecarboxylic acids from turpentine as, for example, sodium permanganate, alkali and alkaline earth dichromates, alkaliferrocyanides, sulfomonoperacid, and the like. Furthermore, ozonation, autooxidation, oxidation with air or oxygen under pressure, in the presence of alkali and catalysts as, for example, manganese salts,

reflux when the acid I electrolysis, etc., may be employed; but for securing high yields of terpenecarboxylic acids, intermediate compounds such as alcohols, glycols and aldehydes may have to be subjected to a reoxidation.

EXAMPLE II Ethoccy ethyl easier 0 pinonic acid,

g. of crude pinonic acid (from Example I) and an excess of ethyleneglycolmonoethylether and 0.01% of benzene sulfonic acid as a catalyst were refluxed as described in Example I. After about eighty hours of heating, the acid number was 23. The brownish oil was dissolved in ether, washed with aqueous sodium bicarbonate and water. The residue was fractionated in vacuum after removing the ether. About ll g. were collected of the fraction boiling at 120.5-121.5 C. (IOU-150 refractive index, n =l.45'79,

specific gravity, d4 =l.0l969, melting point of the semicarbazone IO-72 C.

EXAMPLE III n-Heznyl ester of solid pinonic acid 1103 g. crude pinonic acid, prepared in the same manner as described in Example I was subjected to fractional distillation under reduced pressure at about 11-44 mm.:

Boiling Frac- Yield on P oiit, Remarks 1... 30-159 53. 8 A brownish slightly viscous oil. 2. 159-175 94. 7 Partly crystalline light viscous oil. 3. 176-179 404. 5 Crystalline light yellow oil. 4.... 184-187 327. 1 D0.

27. 6 Partly crystalline.

5-.-... 192-199 140. 6 Residue.

54. 7 Distillation loss.

Fractions 3 and 4 were combined and separated by filtration into 247 g. solid pinonic acid and 452.8 g. liquid pinonic acid, which upon refractionation at reduced pressure, yielded additional 58 g. of solids.

The solid pinonic acid was recrystallized from ethanol and then from water; melting point 102-104 C. (absorption max. at 283 m (D 1.09 (in ethanol); inactive in chloroform solvent. The semicarbazone of dl-pinonic acid melted at 207 C. The characteristics of this acid agree with those given in the literature for dipinonic acid. 50 g. solid dl-pinonic acid was refiuxed for approximately 16 hours with 54 g. nhexyl-alcohol (boiling point l54.2--l55.2 C.) until about the theoretical amount of water had collected in the water trap. The resultant 46.2 gms. of the hexyl ester of (ll-pinonic acid showed the following characteristics: boiling point 141.5" C. (55-60 optically inactive; refractive index, n =l.4542; a 1.4561; specific gravity d4 =0.90533; molecular refraction, found: 74.42, calculated 75.43. Analysis. Calculated for CIGHZSOBI C, 71.64%; H, 10.45%. Found: C. 70.93%, 70.93%; H, 10.21%, 10.00%. Semicarbazone: melting point 97 C.

EXAMPLE IV Hexyl ester of liquid pinonic acid 70 g. liquid pinonic acid ([a] =+15.07 in alsummon cohol; d4 =1.07667; n =1.4682; semicarbazone M. P. 197-198 9.), prepared from fractions 3 and n-hexyl-alcohol in the same manner as described for dl-pinonio acid. The yield of the n-hexylester of liquid pinonic acid was 47.5 g.: boiling point 113-114" C. (260,44); refractive index, 12 1.4534,; n 1.4555; specific gravity, d4 .9623; molecular refraction found: 75.75, calculated for C16H2803,75.43 (a) =+l'2.93 in ethanol. Analysis.-Calculated for the heXy-l ester of pinonic acid Cl6H2803Z C, 71.64%; H, 10.45% for the hexyl ester of pinonic acid 0, 70.87%; H, 10.24%. Found: C, 70.32%; 70.20%; H. 10.26, 9.94%. The semicarbazone of the n-hexylester melted at 100 C.

According to current scientific literature the liquid pinonic acid is a mixture of isomeric pinonic acids, and analogs and homologs of the same, as for example, pinononic acid and pinoylformic acid; this accounts for the slightly lesser carbon and hydrogen content of the ester, as found, by comparison with the calculated values.

EXAMPLE V Esterificatz'on of pinomc acid with Z-ethyZ-hem- (medial-1,3 92 g. liquid pinonic acid 80 g. 2-ethyl-hexanediol-1,3 and 70 g. of xylene were placed in a 500 cc.

round-bottom flask fitted with a reflux condenser and a Dean-Stark water trap containing cc. of xylene; the liquid pinonic acid (a mixture of pinonio, pinononic and pinoylformic acids) was obtained in accordance with the procedure set forth in Example III. The mixture was refluxed at 155-161 C. for approximately 80 hours. The dark brown solution was shaken with a concentrated aqueous solution of sodium carbonate, dried with anhydrous sodium sulfate, filtered and fractioned in vacuum. A mixture of branched ethyl hexane diol esters of liquid pinonic acid was obtained, since the result shows no constant boiling portion.

..n n a j 5u D 1 Yield, (1, a H 33.13., C. Grams Density Remarks 52/32mm. 88.3 Discarded. 98 126/19 23.5 0.95504 lll0/125195;i 18.6 1.033% Plasticizer.

142-155712 14.7 1.03266 30.3 1.01637 25.8 1 01222 24.7 1 01855 7. Residue.

Fraction 3 was employed as a plasticizer for cellulose acetate films. This choice was made because this fraction has the highest density of all fractions obtained and thus appears to be the most uniform in composition of the fractions obtained. The semicarbazone of fraction 3 has a melting point of 187-189 0.; it is in the form of white needles.

The following examples illustrate the production of keto terpene carboxylic acid esters and of the intermediate terpene ketocarboxylic acids from crude sulfate turpentine. The crude sulfate turpentine, which is used as a starting material, is obtained by the condensation of the released gases of the pulp digester used in the sulfate pulp process, a process well known to the art, and described, e. g. in Rogers Industrial Chemistry, vol. 2, 1942, page 1418. The sulfate pulp process essentially comprises the cooking of wood chips in a closed digester in the presence 6. of a cooking liquor composed of sodium hydroxide; sodium sulfide, and sodium sulfate; coniferous: turpentine-rich woods, such as southern pine, are particularly adapted for this process. calcooking operation, the chips are heated with case of turpentine-rich pine wood, which iscu-s" tomarily used in the sulfate process, particularly ture of alpha and beta pinene (approximately 68% alpha pinene and 29% beta pinene) togetherwith quantities (about 3%) of methyl and other mercaptans and other evil-smelling sulfur com-- pounds; this condensation product will behereaf ter referred to as crude sulfate turpentine. Its composition is similar to the composition of the gum spirits of turpentine obtained from southern pine (approximately 70% alpha pinene and 30% beta pinene). On the other hand, the distilled: wood turpentine obtained from southern pine contains almost alpha pinene; the terms lpha pinene and turpentine per se (i. e. distilled turpentine as distinguished from crude sulfate turpentine) will be used interchangeably hereafter.

of the present invention.

The. sulfite pulp process (wherein the wood chips are digested in the containing crude turpentine adulterated with sulfur compounds. Inasmuch as the types of wood customarily used in the sulfite pulp process fite process is ordinarily undersirable for the practice of the present invention. However, it will be understood that if southern pine and other woods whose natural alpha pinene content ap- EXAMPLE VI Pinonz'c acid from crude sulfate turpentine, and cyclohexyl ester therefrom 750 g. crude sulfate turpentine was emulsified 7 by mixing in 15,000 cc. of water, and 1160 g. of was esterfied with an excess of cyclohexanol by potassium permanganate was added with efficient refluxing for approximately 16 hours until about stirring, in portions, during a period of about the theoretical amount of water had collected in four hours. The temperature was kept below the water trap. The crude ester was fractionated 20 C. and the stirring continued for four hours 5 under reduced pressure:

Fraction B. P., 0. Pressure Yield, g. Density ga i Remarks d l 71-151 13-22 mm-.. 34. 3 Odorlcss. Sulfur m 1 4 91 ctesltgositlivelg c o 2 145 190;: 64. c dm=i.02ie2 {ZC J g f J test negative.

Residue.

additional. After standing overnight, the color The cyclohexylester of crude pinonic acid from of the permanganate had disappeared. The man no crude sulfate turpentine (fraction 2) was also ganese dioxide which formed in the reaction was characterized through its semicarbazone: meltremoved by filtration, the precipitate washed with ing point 126-127 C.

water, and the filtrate evaporated in a stream It will be understood that, besides potassium of carbon dioxide until a brown syrup remained. permanganate, ot OXidatiOII ts d This residue was acidified with dilute sulfuric processes enumerated in Example I, above, may acid, whereby the crude terpene carboxylic acids be emp y in the OXidatiOn of crude Su fate turseparated as an upper, oily layer, which was seppentine to keto terpene acids. arated by gravity from the lower aqueous layer EXAMPLE VII containing potassium sulfate and free sulfuric acid The yield was 3375 g. (about by Hescyl ester of pznomc acid from crude sulfate weight of the sulfate turpentine starting ma- 3O turpentine teriai) of crude terpene carbo y i mainly The n-hexyl ester of crude terpene carboxylic crude dl-pinomc acid. The product was dark acids (mainly dl-pinonic acid) was produced as brown in color and crystallized partly on standfollows; ins a IOOm mp 35 319 g. crude terpene carboxylic acids from crude 319 g. of this material was fractionated in sulfate turpentine (Example VI) was frationated vacuum with the following results: under reduced pressure with the following results:

Fraction i g Yield Remarks m l 103460 9.5 33 g. Sulfur test positive. 2 170-181 10 274 g. Semicrystailine mass.

87 g Sulfur test negative.

------------------ {3.3 i'.05% Loss h Fraction 1, a sulfur-contaminated forerun, was Fraction Boiling Point, C. Remarks discarded.

197.49 g. of the main fraction were separated by filtration into 27.5% solid acids and 72.4%

AJLIJ 1 P3 9136 r 131 E i t 'd liquid acids 2 7 8 mm..... em crys pro ggg f f The liquid acid portion showed the following 3.3 Distn. loss. characteristics: Refractive index n =1 4742 density d4 =1.07289; neutr. equiv., 252.6.

A 50 g. portion of the last-mentioned liquid pinonic acid portion was refluxed with n-hexanol until the theoretical amount of water had collected in the Water trap. The resulting n-hexyl The presence or absence of sulfur was ascertained by the sodium fusion procedure using lead acetate as specific reagent for the precipitation of sulfur as m lead u1fide ester of liquid pinonic acid was obtained in a 197' of fra ti 2 were separated by filtra yield of 43.9 g., and had the following constants: de olid d1 pinonic B. 138---145D at refractive index tion into 27.5 per cent of cm 2 acid and 72.4 per cent liquid pinonic acids. The i "n 6161181133 dl-pinonic acid was purified through recrystallization from ethanol and then from water. EXAMPLE VIII Colorless, transparent plates, melting point, 99.5-l0l.5 C. neutr. equiv.: calcd. for a monobasic Benzyl ester of flzgg ggg crude sulfate acid CioHisOs, 184.2. Found: 184.

The liquid portion was optically active [d] 35 g. crude terpene carboxylic acids from Ex- +23.5; d4 l.07289; 11 14742; neutr. equiv.: ample VI were esterfied with benzylalcohol fol- 252.6. lowing the same procedure as described in previ- A g. portion of the unfractionated crude ous examples. The components were refluxed for terpene carboxylic acids (a pinonic acid mixture) 7 about 50 hours at about 200-240" C. The reoxidation of a oxidation product obtained from sultant product was reduced pressure:

then directly fractionated at Equal portions by weight of the crude pinonic acid, produced as just described, and of the Fraction B. Pt, 0. Pressure Yield, g. I Density Refrac. Index Remarks -28 mm.-- 20 mm. 180;; B 1

20:1 5146 enzy ester, a 4 150-152. 5 180p. 26. 5 D =1.06965 pale yellow {7!m 1.5181 liquii 5 Residue.

The benzylester of the crude pinonic acid (fracterpene alcohol mixture,

tion 4) was also characterized through its semicarbazone: melting point 107-108 C.

The following example illustrates the production of esters of crude keto terpene carboxylic acids and terpene alcohols, both produced from alpha pinene (turpentine). The essence of this process is (1) the oxidation of alpha pinene (turpentine) to form terpene alcohols, (2) the further portion of the terpene alcohols to form terpene carboxylic acids, and (3) the formation of esters by reacting the terpene alcohols with the terpene carboxylic acids. Continuous extraction with chloroform is utilized in the production of the acids.

EXAMPLE IX Pinonz'c acid produced by continuous extraction,

and its terpenyl ester acted, and the manganese dioxide formed in the reaction was filtered off. The clear aqueous filtrate was light brown in color. Four batches were combined and extracted with chloroform. The yield was 40.4 g. of a brownish-colored viscous oil, which had the following properties: density (14 1.08147; refraction index n 1.48712.

produced as described in the first paragraph of this example, were esterified, using xylene as the water carrying-oil reagent. After 40 hours of reflux, approximately of amount of water calculated had been given off. An additional 40 hours of heating and in the presence of 0.01% of benzenesulfonic acid, a total amount of 150% of water calculated was collected. The resultant dark brown oil was dissolved in ether and the ether solution extracted with dilute sodium bicarbonate solution for removing the excess pinonic acid. After washing with water and drying the ether solution with anhydrous sodium sulfate, the ether was removed by distillation and the residue fractionated at reduced pressure. The main fraction, terpenyl ester of crude pinonic acids, was a red dish colored oil; boiling point 118-184" C. (260 refractive index, n =1.493'0; n =1.4918; density, d4 =1.04315. A principal-use of the terpenyl ester of crude pinonic acid is as a plasticizer, e. g. for cellulose acetate and cellulose propionate.

The following examples illustrate the production of various new esters of terpene carboxylic acids other than pinonic acid.

EXAMPLE X Texg Z diester of camphem'c acid 70 g. of camphenic acid were esterified with an excess of n-hexyl alcohol by refluxing until approximately the theoretical amount of water had collected in the water trap. The product was fractionated at reduced pressure.

Fraction B. Pt., 0. Pressure, c Yield, g Refrac. Index Density Remarks 1 153157.5 160 10 2 156 5-1515 165 70. 5 z jfgg }d, =o.9573 {1333 31 3553 3 Residue.

This product is a non-acidic mixture of cycloaliphatic terpene alcohols and glycols.

One half of this viscous oil was made acid with dilute sulfuric acid to about pH 5.5 and subjected to continuous countercurrent extraction with chloroform as follows: The aqueous solution was introduced at the bottom by gravity feed of an extraction column and chloroform was introduced at the top. The extracted aqueous terpenic acid layer was continuously drawn off at the top and collected in a receiving vessel. The chloroform, which formed a layer at the bottom portion of the extraction column, was continuously drawn off at the bottom and fed to a refluxing still in which it was continuously distilled and returned to the column at the top. The oxidation products, a brownish semi-solid mass, neutr. equiv. 216.3, were identified as con taining principally crude pinonic acid; they containedmore solids (oil-pinonic acid) than the alpha pinene with an alkaline permanganate solution according toExample I.

Fraction 2 was analyzed. Calculated for C22H4o04: C, 71.74%; H, 10.87%. Found: C, 72.70%, 72.24%; H, 11.16%, 11.00%. Molecular refraction, calculated: 104.47; found: 104.51. The resulting product is thus identified as the n- Hezryl ester of vcczmphenom'c acid 10 g. of camphenonic acid were esterified with an excess of n-hexyl alcohol, as described in preceding example. 9.5 g. of the n-hexyl ester of camphenonic acid were obtained. The ester had the following characteristics: boiling point 151- 151.5 C./250 refractive index n :'1.4649; density, d4' :l.00-1.54. Analysis-calculated Esterification of nopim'c acid with n-hemyl alcohol 25 g. of nopinic acid (M. P. 129 C.) and 100 cc. of n-hexyl alcohol and 0.02% benbenesulfonic acid was refluxed while collecting water which was split off in the course of the reaction. After heating for 21 hours, 2.23 mols of water were formed. The reaction mixture was fractionated in vacuum with the following results:

Fraction .232 5 Pressure g Reli r scilcetive Molecular refraction of fraction 8 was 73.67. Inasmuch as over twice as much water was split off during the reaction than was calculated for the formation of the n-hexyl ester of nopinic acid by direct esterification, it is postulated that an internal dehydration also took place in the bicyclic terpene ring and that the monocyclic n-hexyldihydrocuniate was formed. The calculated molecular refraction of n-hexyl dihydrocumate (74.63) agrees with the value actually found (73.67) for fraction 3.

EXAMPLE XIII Hemyl diester of camphoric acid (direct esterification) 225 g. of d-camphoric acid (M. P. 187 C.) ([al =+47.l in ethanol), 248 g. of n-hexyl alcohol and 0.1% of benzenesulfonic acid were refluxed for 64 hours at a temperature of about 135-145 C. After an additional 50 g. of n-hexyl alcohol were added, the mixture was heated for hours. Altogether approximately two moles of water were removed during the reaction. The crude n-hexyl diester of d-camphoric acid was fractionated under reduced pressure at 2.4 mm. The first fractions were discarded and the remaining fraction of about 190 g. having a boiling point of about 183 C. was refractionated at high vacuum with the following results:

Density Density Residue.

1 2 Structural formula of the n-hexyl diester of d-camphoric acid:

CH3 HzC-( JC O O CeHu H30 0 on.

HzC-C-C O O CuHn The n-hexyl diester of d-camphoric acid may also be produced from the silver salt of d-camphoric acid and hexyl iodide as follows:

EXAMPLE XIV camphoric acid (alternate method) g. of d-camphoric acid were suspended in a minimum of water and made slightly alkaline by adding a 10% aqueous solution of sodium hydroxide. An aqueous solution containing about 10% more than the calculated amount of silver Hem/Z diester of Remarks nitrate, 190 g. was added, the precipitated disilver salt of camphoric acid was filtered off and washed with water. The brownish silver salt was covered with about a 10% excess of n-hexyl iodide, after removing excess water by drying in vacuum. After the ensuing exothermic reaction, the mixture was then heated in a water bath at about 75 C. for 22 hours. After separating the silver iodide formed in the reaction by filtration, the precipitate was washed with alcohol, and the filtrate distilled with steam to remove unreacted n-hexyliodide. The residue from the steam distillation was dissolved in ether and the ether solution treated with aluminum amalgam overnight, in order to remove all traces of iodine. The aluminum oxide was filtered off, the ether solution washed with dilute sulfuric acid and then with water. After evaporation of the ether, 124.8 g. of the residue was fractionated in vacuum. The first fractions were discarded be cause of separation of camphoric anhydride, and the main fraction consisting of n-hexyl di-ester of d-camphoric acid was collected: boiling point, -171 C. at 125p. pressure; yield 54 g.; refractive index n =0.96923.

'70 g. n-hexanol and 12.6 g. metallic sodium Opt. Rot.

.Fractlon B. 1%., 0. Pressure, 1 Yield, g. Reirac. Ind. 1 152-165 68 h 2 159-161. a 65-68 147. 3 {221 3 1233 Fraction 1 contained camphoric anhydride. Fraction 2 was identified as the pure n-hexyl diester of d-camphoric acid. Molecular weight calculated for C22H40O42104A'7. Found, 104.46.

ethanol.

0 Residue.

were gently heated. After the disappearance of the sodium, 100 g. d-camphoric anhydride were added and the mixture heated under reflux for 6 hours at C. The product was then dis- '13 solved in 1000 cc. of water. was extracted with ether to remove unreacted starting materials and then acidified with dilute sulfuric acid. The hexyl monoester of d-"cam- "The aqueous solution Below 79 0.. Below 75 0..... Below 79 0.....

Hcxyl ester of liquid pinonic acid.... Hexyl diester of camphoric acid Hexyl diester of camphenic acid. Commercial Plasticizcrs: Butylphth alate Methylphthalate Santicizer E-l5 (ethyl phthalylethyl I glycollate) Santicizer ill-l7 (methyl phthalyl ethyl glycollate).

The tests for evaluating the performance of terpene carboxylic acid esters of the present invention as plasticizers for various cellulose and synthetic resin films fully bore out the expectations raised by their favorable pour point characteristics. The tests were carried out by preparing a stock solution of 70 g. of the cellulose ester or resin in 1000 of organic solvent, and adding the plasticizers in the ratio of 1 part of plasticizer to 4 parts of stock solution (except in the case of polystyrene to which the plasticizers were added in the ratio of 1:3). g. portions of each plasticized solution were poured into Petri dishes of 9.5 'cm. diameter, and the solvent was allowed to evaporate over a period of approximately 3 days.

Per cent shrinkage was computed after formation of the film by determining the ratio of the uncovered area of the Petri dish with its total area. Percentfshi-inkage :ofless than 3% :should be considered negligible in actual practice.

Flexibility at room temperature (20 C.) was determined by folding 1 sq. cm. of the .film on an phoric acid separated as an oily upper layer. 5 aX isi-first in one direction and then in the op- This was taken up in either, the ether solution posite direction. The Jfilm is folded again on an washed with water and dried with anhydrous axis which perpendicular to the first axis in sodium sulfate. After distilling oil the ether, the one direction and then 'againxin the opposite diresidue, 134.7 g., was fractionated in high vacrection. Any break in the film caused it to be uum. The main fraction, g., B. P. -187C., l0 consideredi'noneflexible. To determine the flexwas a semi-solid'ma'ss, ibility below -501C 1 sq. cm. of the film was Unreacted d-camphoric anhydride Was replaced in a test tube, which was immersed in a moved from this mass by dissolving the latter in ya t e a A e p d Of DD ether and extracting the ether solution with soy'fi minutes, e fi W s te ted fo lex-- dium carbonate. The ester was then regenerated 15 ibility a p v ou ly described. from the sodium carbonate solution (yield (a) The fDIlOWiIIg results e e Obta ed With 76.4 g,) and redistillecL The purified hexyl Cellulose Acetate PM-3 (Hercules Powder Com- .monoester of d-camphoric acid was obtained in p y a yield of 47 g.; boiling point 196-206 C1325 Clear fi with h nkage of 0 2%, and flexdensity d4 =l.0350; index of refraction 29 ilole at and below y the addin =1.4702; neutr. equiv, calculated for mono- 151011 of! basic acid ClSHESO4 284.4; found 269. Structural .diester of camphoric acid -P the n'hexyl monoester of n-I-Iexyl ester of pinonic acid (source: liquid "phone acld: pinonic acid from alpha pinene) CH3 Cyclohexyl ester of pinonic acid obtained from crude sulfate turpentine (film not flexible at 50 C.) HaCCCHs Benzyl ester of pinonic acid obtained from'cru'de mo-g-ooomrm 30 sulfate turpentine Ethoxyethyl ester *of pinonic acid A highly valuable property of the esters of terpene carboxylic acids produced in accordance (b) The fOlIOWing u t We e b ai d with with the preceding examples, and f number of Cellulose Triacetate -TH-2 (Hercules Powder their homologs and analogs is their low pour Company): point (freezing point), which enables their use q I H as plasticizers for cellulose acetate films and ggg g i g g gg i other polymers, and rubber, for use 1n arctic tion climates. The following table shows the pour points of a number of these esters, and compares 40 n-I-Iexyl diester of camphemc acid them with the pour points of a number of conn-Hexyl ester of oil-pinonic acid (solid pinonic ventional non-terpenic plasticizers. acid from alpha 'pinene) Pomi gg g Remarks Terpene Carboxylic Acid Esters: I Benzyl ester of pinonic acid 52 C Hcxyl ester of dl-pinonic acid Below 76 0"...

: Crystalline.

Do. N 0 longer plastic.

n-Hexyl monoester of 'camphoric acid n-Hexyl ester of pinonic acid (liquid pinonic acid from alpha pinene) Benzyl ester of pinonic acid Ethoxyethy-l ester of pinonic acid (0) The following .results were obtained with Cellulose Prop'ionateFormula No. 28251 (Celanese Corp).

Clear films with shrinkage of 02.%, and flexible at 20 C. and below '5'0' C. by the addition of:

n-nexyi ester of pinonic acid (liquid pinonic acid from crude sulfate turpentine) Benzyl ester of pinonic acid (from crude turpentine) Benzyl ester of pinonic acid (from alpha pinene) Ethoxyethyl ester of pinonic acid 2-ethyl-hexanediol-1,3 ester of pinonic acid Nopinic acid esterified with n-hexyl alcohol n-Hexyl ester of camphenic acid Liquid pinonic acid esterified with terpene alcohol obtained by oxidation of alpha pinene (not flexible at -50 C.)

(d) The following results were obtained with Polystyrene 5110-P8 (Koppers Co.)

Clear films with shrinkage of -2%, and fiexible at C. (the films were not flexible at -50 C.), by the addition of:

sulfate n-Hexyl monoester of camphoric acid n-Hexyl diester of camphoric acid n-Hexyl diester of camphenic acid n-Hexyl ester of dl-pinonic acid (solid pinonic acid, from alpha pinene) n-Hexyl ester of pinonic acid (liquid pinonic acid from alpha pinene) n-I-Iexyl ester of pinonic acid (liquid pinonic acid from crude sulfate turpentine) Cyclohexyl ester of pinonic acid fate turpentine) Benzyl ester of pinonic acid (from alpha pinene) (e) The following results were obtained with polyvinyl butyral:

Clear films with shrinkage of 0-2 and flexible at 20 C. and below 50 C., by the addition of:

n-I-Iexyl monoester of camphoric acid n-I-Iexyl diester of camphoric acid n-I-Iexyl diester of camphenic acid n-I-Iexyl ester of dl-pinonic acid (solid pinonic acid, from alpha pinene) n-Hexyl ester of pinonic acid (liquid pinonic acid from alpha pinene) n-Hexyl ester of pinonic acid (liquid pinonic acid from crude sulfate turpentine) Cyclohexyl ester of pinonic acid (from sulfate turpentine) Benzyl ester of pinonic acid (from alpha pinene) In comparative tests to determine the effectiveness of a commercial plasticizer on cellulose esters at low temperatures it was found that Cellulose Acetate PlVL-3, Cellulose Triacetate TH-Z, and Cellulose Propionate Formula Number 28,251, each plasticized with Santicizer E-15 (ethyl phthalyl glycollate) in the ratio of one part of plasticizer to 4 parts of cellulose ester yielded a film that was non-flexible at -50 C. The same results were obtained by the addition of Santicizer lVI-l'? (methyl phthalyl ethyl glycollate) in the same proportions.

In a test for fungistatic properties of a film plasticized with terpene carboXylic acid ester, sterile and non-sterile cellulose films, plasticized with the n-hexyl ester of pinonic acid were inoculated with a Wellman, McCallan, spore suspension. The plasticized cellulose acetate films were not attacked by fungi after 14 days incubation at 85 to 90 relative humidity.

In a comparative test for the fungistatic properties of terpene carboxylic acid esters, they were added to Czapeks agar solution (concentration of 250 p. p. m.) the solutions were placed on test plates, inoculated with Aspergzllus nzger, TC215-4247, and incubated for 96 hours at 85-90 F. and 85-90% relative humidity. The results (from crude sulcrude 16 were computed in terms of per cent of inhibition, based on the average diameter of the fungus colonies of the test plates as compared to that of the untreated controls. The results are shown in the following table:

TABLE 1 Compound n-Hexyl ester of (ll-pinonic acid (solid pinonic acid,

from alpha plnene) n-Hcxyl ester oi liquid pinonic acid Bcnzyl ester 01' pinonic acid These results are superior to results obtained with conventional iungistatic agents:

Bcnzoic acid n-Hexyl benzoatc Salicylic acid While I do not desire to limit myself to any particular theory as to the reason for the plasticizing efiectiveness of the esters of terpene carboxylic acids in accordance with the present invention, it may be that, particularly in the case of the higher esters of camphoric acid such as the n-hexyl diester of camphoric acid, a migration takes place in situ with the formation of the anhydride (e. g. d-camphoric anhydride which is an exceedingly effective plasticizer).

In addition to the usefulness of the terpene carboxylic acid esters, as disclosed herein, as plasticizers for cellulose esters and resins of the type obtained by the polymerization of a monomer containing a polymerizable CI-IztCH- group (such as for instance polystyrene or polyvinyl butyral), they can also serve as plasticizers for natural and synthetic rubbers, as pour point depressants for low temperature lubricants, brake fluids, and leather greases. Their desirable fungistatic properties can be utilized in adhesive compositions, as fixatives in soaps and lotions, as pigment carriers in paints, in protective coatings and lacquers, and other applications.

It will be understood that the various examples given herein are illustrative of specific instances of the production and utilization of terpene carboxylic acid esters in accordance with the present invention, and are not intended to limit the scope of my invention to the particular details set forth in such examples. Inasmuch as variations and modifications within the spirit of my invention will be readily apparent to the expert, I intend to encompass such variations and modifications within the scope of my appended claims.

I claim:

1. An ester of a monocyclic keto terpene carboxylic acid being a member of the group consisting of pinonic acid and pinoylformic acid, wherein the esterifying group is an ester-forming radical of a liquid alcohol of the type A(OH) n, n being an integer not less than 1 and not more than 2, and A being a member of the group consisting of an aliphatic hydrocarbon radical having at least 6 carbon atoms, an aliphatic ether radical having at least 4 carbon atoms, a cycloaliphatic hydrocarbon radical, and an aromatic hydrocarbon radical wherein the benzene ring is linked to the alcoholic hydroxyl group by a methylene group.

2. An ester of pinonic acid, wherein the esterifying group is an ester forming radical of a liquid alcohol of the type A(OH)n, n being an integer not less than 1 and not more than 2, and A being a member of the group consisting of an aliphatic hydrocarbon radical having at least 17 6 carbon atoms, an aliphatic ether radical having at least 4 carbon atoms, a cycloaliphatic hydrocarbon radical, and an aromatic hydrocarbon radical wherein the benzene ring is linked to the alcoholic hydroxyl group by a methylene group.

3. The n-hexyl ester of pinonic acid.

4. An ester of pinonic acid and of a liquid monohydric alcohol, said alcohol being characterized by a saturated hydrocarbon chain having 6 carbon atoms.

5. The ethoxyethyl ester of pinonic acid.

6. The ester of pinonic acid and 2-ethylhexanediol-1,3.

7. The benzyl ester of pinonic acid.

8. A method of preparing 2,2-dimethyl cyclobutane keto terpene carboxylic acid esters, comprising reacting crude sulfate turpentine which contains predominantly alpha-pinene contaminated by malodorous organic sulfur compounds, with an oxidizing agent which does not split the 2,2-dimethyl cyclobutane ring of said alphapinene, removing the solid reaction products, acidifying the liquid residue whereby a sulfurcontaminated 2,2-dimethyl cyclobutane keto terpene carboxylic acid layer is formed, separating said acid layer, esterifying the same, and desulfurizing the ester.

9. The method according to claim 8, wherein said oxidizing agent is an alkali metal permanganate.

10. A method of preparing 2,2-dimethyl cyclobutane keto terpene carboxylic acids, comprising reacting crude sulfate turpentine which contains predominantly alpha-pinene contaminated by malodorous organic sulfur compounds, with an oxidizing agent which does not split the 2,2- dimethyl cyclobutane ring of said alpha-pinene, removing the solid reaction products, acidifying the liquid residue whereby a sulfur-contaminated 2,2-dimethyl cyclobutane keto terpene carboxylic acid layer is formed, and desulfurizing said 2,2-dimethyl cyclobutane keto terpene carboxylic acid.

11. A continuous process of preparing pinonic acid, comprising reacting crude sulfate turpentine which contains predominantly alphapinene contaminated by malodorous organic sulfur compounds, with an oxidizing agent which not split the 2,2-dimethyl cyclobutane ring of said alpha-pinene, removing the solid reaction products, acidifying the liquid residue, continuously extracting the acidified liquid in countel-current with a water-immiscible organic solvent, continously separating said solvent, and

fractionating the sulfur-contaminated residue into a sulfur-containing forerun and at least one main fraction principally containing solid and liquid pinonic acids.

12. A continuous process of preparing pinonic acid, comprising reacting crude sulfate turpentine which contains predominantly alpha-pinene contaminated by malodorous organic sulfur com pounds, with potassium permanganate in the presence of ammonium sulfate, removing the solid reaction products, acidifying the sulfur contaminated liquid residue to a pH of about 5.5, extracting and purifying acidified liquid in countercurrent with chloroform, continuously removing said chloroform, purifying said chloroform 18 and returning the purified process.

13. A method of preparing pinonic acid, comprising reacting crude sulfate turpentine which contains predominantly alpha-pinene contaminated by malodorous organic sulfur compounds, with an oxidizing agent which does not split the 2,2-dimethyl cyclobutane ring of said alphapinene, removing the solid reaction products, acidifying the liquid residue, extracting the acidified liquid with a water-immiscible organic solvent, separating said solvent, and fractionating the sulfur-contaminated residue into a sulfur containing fore-run and into at least one main fraction principally containing pinonic acid.

14. A method of preparing a 2,2-dimethyl cyclobutane keto terpene carboxylic acid ester, comprising esterifying a 2,2-dimethyl cyclobutane keto terpene carboxylic acid obtained from chloroform to the said liquid residue into two portions, acidifying is obtained, and esterifying the pinonic acid thus formed by reacting it with the other portion of said liquid residue.

16. An ester of pinonic acid, wherein the esterifying group is the radical of a cycloaliphatic terpenyl alcohol obtained by the oxidation of pinene.

17. An alkoxyethyl ester of pinonic acid, wherein the alkoxyethyl radical has at least 4 carbon atoms.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 577,302 Hesse Feb. 16, 1897 707,278 Summers Aug. 19, 1902 2,062,144 Barrett et al. Dec. 8, 1936 2,333,718 Heisel Nov. 9, 1943 2,360,898 Sarbach Oct. 24, 1944 2,394,952 Vincent Feb. 12, 1946 2,396,264 Huffman Mar, 12, 1946 2,407,937 Rummelsberg Sept. 17, 1946 2,427,344 Bain Sept. 16, 1947 OTHER REFERENCES Beilstein, Vierte Auflage, vol. 9, pages 752, 753, 744 and 745.

Beilstein, vol. 10, pages 622-625 and 32.

Beilstein, Vierte Auflage, 1st supplemental, vol. 9, pages 322 and 323.

Cohen: J. Chem. Soc. 109, 222235 (1916).

Beilstein, 4th ed. (1927), page 617.

Schoene: Arch. Exptl. Path., Pharmacol. 190. 372-5 (1938). 

1. AN ESTER OF A MONOCYCLIC KETO TERPENE CARBOXYLIC ACID BEING A MEMBER OF THE GROUP CONSISTING OF PINONIC ACID AND PINOYLFORMIC ACID, WHEREIN THE ESTERIFYING GROUP IS AN ESTER-FORMING RADICAL OF A LIQUID ALCOHOL OF THE TYPE A (OH)N, N BEING AN INTEGER NOT LESS THAN 1 AND NOT MORE THAN 2, AND A BEING A MEMBER OF THE GROUP CONSISTING OF AN ALIPHATIC HYDROCARBON RADICAL HAVING AT LEAST 6 CARBON ATOMS, AN ALIPHATIC ETHER RADICAL HAVING AT LEAST 4 CARBON ATOMS, A CYCLOALIPHATIC HYDROCARBON RADICAL, AND AN AROMATIC HYDROCARBON RADICAL WHEREIN THE BENZENE RING IS LINKED TO THE ALCOHOLIC HYDROXYL GROUP BY A METHYLENE GROUP. 